/*
 * Copyright 2018, Jérôme Duval, jerome.duval@gmail.com.
 * Distributed under the terms of the MIT License.
 */
#ifndef _KERNEL_ARCH_x86_ALTCODEPATCH_H
#define _KERNEL_ARCH_x86_ALTCODEPATCH_H


#include <arch/x86/arch_kernel.h>


#define X86_NOP1        0x90
#define X86_NOP2        0x66, 0x90
#define X86_NOP3        0x0f, 0x1f, 0x00
#define X86_NOP4        0x0f, 0x1f, 0x40, 0x00
#define X86_NOP5        0x0f, 0x1f, 0x44, 0x00, 0x00
#define X86_NOP6        0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00
#define X86_NOP7        0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00
#define X86_NOP8        0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00
#define X86_NOP9        0x66, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00


#define ALTCODEPATCH_TAG_STAC           1
#define ALTCODEPATCH_TAG_CLAC           2
#define ALTCODEPATCH_TAG_XSAVE          3
#define ALTCODEPATCH_TAG_XRSTOR         4
#define ALTCODEPATCH_TAG_CLEAR_FPU      5


#ifdef _ASSEMBLER

#define CODEPATCH_START 990:
#define CODEPATCH_END(tag)      991:    \
        .pushsection    .altcodepatch, "a"      ;       \
        .long                   (990b - KERNEL_LOAD_BASE)       ;       \
        .short                  (991b - 990b)           ;       \
        .short                  tag                             ;       \
        .popsection

#define ASM_STAC        CODEPATCH_START \
                                        .byte X86_NOP3  ;        \
                                        CODEPATCH_END(ALTCODEPATCH_TAG_STAC)

#define ASM_CLAC        CODEPATCH_START \
                                        .byte X86_NOP3  ;       \
                                        CODEPATCH_END(ALTCODEPATCH_TAG_CLAC)

#else

#define _STRINGIFY(x...)        #x
#define STRINGIFY(x...)         _STRINGIFY(x)

#define CODEPATCH_START "990:   \n"
#define CODEPATCH_END(tag)      "991:   \n"     \
        ".pushsection   .altcodepatch, \"a\"    \n" \
        ".long                  (990b - " STRINGIFY(KERNEL_LOAD_BASE) ")        \n" \
        ".short                 (991b - 990b)           \n" \
        ".short                 " STRINGIFY(tag)        "       \n" \
        ".popsection"

#define ASM_STAC        CODEPATCH_START \
                                        STRINGIFY(.byte X86_NOP3)       "\n" \
                                        CODEPATCH_END(ALTCODEPATCH_TAG_STAC)

#define ASM_CLAC        CODEPATCH_START \
                                        STRINGIFY(.byte X86_NOP3)       "\n"\
                                        CODEPATCH_END(ALTCODEPATCH_TAG_CLAC)


void arch_altcodepatch_replace(uint16 tag, void* newcodepatch, size_t length);


#endif

#endif  /* _KERNEL_ARCH_x86_ALTCODEPATCH_H */